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Meta-analysis: LMWH decreased risk for VTE in ambulatory cancer patients
51st ASH Annual Meeting
Low molecular weight heparin prophylaxis was effective and led to a 46% reduction in relative risk for venous thromboembolism in outpatients with cancer. Yet, concerns remain about the increase in major bleeding events, according to results from an updated meta-analysis of LMWH prophylaxis.
“There is a need to weigh the risks and benefits of routine VTE prophylaxis and therefore prophylaxis cannot be recommended at this time,” Nicole M. Kuderer, MD, a fellow in hematology, oncology and cellular therapy at Duke University in Durham, N.C., said during a presentation at the 51st ASH Annual Meeting. “As studies are ongoing to better identify cancer outpatients at risk for VTE, a thromboprophylaxis may have a more favorable risk benefit ratio.”
Researchers conducted a systematic review of eight randomized, controlled trials that included outpatient data for people with cancer. They found that the untreated patients were nearly twice as likely to develop blood clots, when compared with those who took heparin.
The studies included patients randomly assigned to LMWH for VTE prophylaxis (n=1,685) or no treatment (controls; n=1,275) and reported rates for VTE as the primary or a secondary outcome. Three studies included various solid tumors and one study included breast cancer, lung cancer, pancreatic cancer and glioblastoma.
According to the researchers, “most trials did not require VTE screening by imaging, which prevented additional analysis of VTE events.”
VTE events
Patients assigned to LMWH had 47 VTE events vs. 74 events in the control group (2.79% vs. 5.8%).
The overall RR for VTE was about 0.54; RR for VTE for the five primarily prophylaxis studies was 0.50 with an estimated decrease in absolute risk of 2.95% (P<.001 for all).
RR for VTE in patients with pancreatic cancer was 0.36. A higher dose of LMWH reduced VTE by an AR of 13%.
Major bleeding events were reported in 30 patients assigned to LMWH vs. 15 patients assigned to the control group (1.78% vs. 1.18%). The RR for major bleeding in the five primary prophylaxis studies was 2.27 (P=.022) and a 1.27% increase was observed for absolute risk (P=.013).
Overall RR for major bleeding was estimated at 1.74 (P=.071); a 0.75% increase was observed for absolute risk (P=.011).
However, Kuderer said they also found a significantly better risk/benefit ratio of anticoagulant use among patients with pancreatic cancer. "These patients are at significantly higher risk of developing blood clots to begin with. Using anticoagulants in this group led to a 13% reduction in clots. Since the major bleeding risk in that group was also just under 1%, it strongly suggests that routine use of blood thinners in this group makes sense," she added. – by Jennifer Southall
For more information:
- Kuderer. #490. Presented at: 51st ASH Annual Meeting and Exposition; Dec. 5-8, 2009; New Orleans.
